1. Field of the Invention
The invention relates to hardening of steel.
2. Description of Prior Art
The invention relates more particularly to surface or full hardening of carbon steel. Generally stated it is usual to harden steel or especially outer surfaces of steel or steel members to achieve high hardness and good wear resistance after the member has been formed or shaped as required. Hardened steel surfaces are exceptionally difficult to work (e.g. machine) and so hardening is carried out on a finished or a nearly finished product normally. Hardening is typically carried out by heating the steel member (except for low carbon steel) to a high temperature and quenching the member exceeding its critical cooling rate. Hence the hardening equipment and operating costs are inherently high.
Three Russian papers (Yarsnogorodski, 1954a, b & c) and one Chinese paper (Yan et al, 1994) have proposed hardening of steel by direct current (d.c.) electrolysis in which caterpillar track pins, roller hoops, piston rings, rockers, camshaft, taps and drills were surface hardened. The results were however not stable.
The applications of pulse current in electrodeposition has been described in U.S. Pat. No. 4,789,437 (Miu et al).